This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-099625, filed Apr. 7, 1999; and No. 11-275746, filed Sep. 29, 1999, the entire contents of which are incorporated herein by reference.
The prior art position measurement apparatuses using a GPS (Global Positioning System) that utilizes position measurement satellites measure the present locations by receiving navigation signals or position measurement information such as Ephemeris and Almanac. Ephemeris provides data denoting the orbit information of satellites and clock correction information whereas Almanac supplies data denoting the approximate orbit information of all GPS satellites. To receive the position measurement information, each satellite is acquired by synchronizing the data receiving timing to the data transmitting timing from the satellite, and the accuracy of positioning increases as the number of satellites that are acquired increases.
However, when the above-mentioned position measurement apparatus is incorporated in a portable device such as a wristwatch, the following problems occur. Since receiving position measurement information for the above-mentioned position measurement operation consumes much more electric power than the simple clock operation of the wristwatch, the life of batteries is shortened, which requires a greater capacity of battery and a larger size of the device deteriorating its portability.
The object of the present invention is to solve these problems and provide a position measurement apparatus of a smaller size with a longer life of batteries.
One preferred embodiment of the present invention is a position measurement apparatus that detects location by receiving external signals, comprising:
a position measurement unit that receives position measurement information transmitted from satellites and measures the present location based on the information;
a timer that measures time;
a judging unit that judges whether the device is in a stationary condition for a specified period of time; and
a control unit that ends a position measurement operation for the present location by the position measurement unit according to judgment made by the judging unit that the device has remained stationary for a specified period of time.
Another preferred embodiment of the present invention is a position measurement apparatus that detects location by receiving external signals, comprising:
a position measurement unit that receives position measurement information transmitted from satellites and measures the present location based on the information;
a memory unit that successively stores the present location measured by the position measurement unit; and
a control unit that prohibit to store new present location data in the memory unit while the present location measured by the position measurement unit is outside a predetermined area.
Still another preferred embodiment of the present invention is a position measurement apparatus that detects location by receiving external signals, comprising:
a position measurement unit that receives position measurement information transmitted from satellites and measures the present location based on the information;
a memory unit to store a predetermined area; and
a control unit that specifies the receiving interval of the position measurement unit for the position measurement information longer, if the present location measured by the position measurement unit is outside the area stored in the memory unit, than the interval applied to the area stored in the memory unit.
Yet another preferred embodiment of the present invention is a portable position measurement apparatus that can be worn by the user, comprising:
a position measurement unit that receives position measurement information transmitted from satellites and measures the present location based on the information;
a wearing situation detection unit to detect wearing situation by the user of the device; and
a control unit that ends the measurement of the present location by the position measurement unit in accordance with the detection of non-wearing situation by the detection unit.
A further preferred embodiment of the present invention is a portable position measurement apparatus that can be worn by the user, comprising:
a position measurement unit that receives position measurement information transmitted from satellites and measures the present location based on the information;
a wearing situation detection unit to detect the wearing situation wherein the device is worn by the user; and
a control unit that starts measuring the present location by the position measurement unit in accordance with the detection of wearing situation by the wearing situation detection unit.
In any of the above embodiments, it is possible to save the electric power consumption by the device without significantly affecting the convenience of use, and a longer life of batteries and a smaller size of the device are obtained.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.